Inflator

ABSTRACT

The present invention provides an inflator in which rupturing ability of a rupturable plate is improved. An igniter 26 accommodated in a diffuser portion 20 has, on a peripheral face of a cup 28 covering an igniting portion, a hole 29 covered with a sealing tape from the inside of the cup, and the hole 29 is exactly opposite to the rupturable plate 19. When the igniter 26 is actuated, a rupturing energy is intensively discharged from the hole 29 to the rupturable plate 19, so that the rupturing ability of the rupturable plate 19 can be improved.

TECHNICAL FIELD WHERE THE INVENTION BELONGS

The present invention relates to an inflator suitable for an air bagsystem for an automobile.

BACKGROUND ART

As an inflator for an inflating type safety system of an automobile, inorder to optimally protect a passenger in accordance with a position ofa seat in a vehicle such as a driver side, a passenger side and thelike, various inflators are generally used. As the inflators, there havebeen known ones where such a pressurized gas as argon, helium or thelike is used as an inflating means for an air bag.

In such an inflator, since outflow of a pressurized gas is started byrupture of a rupturable plate and an air bag is inflated and developedfinally, it is important to improve the rupturing ability of therupturable plate for enhancing an activation reliability of theinflator. Further, a structure of the inflator is required to besimplified as much as possible in order to meet a demand for size andweight reduction. Besides, there is a demand for simplification of anassembling process or the like.

In JP-A 2002-172995, there is disclosed an invention relating to astored gas inflator. In FIG. 2 showing the invention, a main chamber 20and a small chamber 18 are formed, a communication hole 26 and a smallhole 28 are formed in a separation wall 24 disposed between thesechambers, and rupturable plates (first and second burst shims) 16 and 22are mounted to a gas ejecting hole 14 formed in the small chamber 18 andthe communication hole 26. An initiator 30 is provided in a pressurizedatmosphere inside the small chamber 18, and in the description of thepublication, it is described that the rupturable plate can be rupturedeven by an igniter with a small output. However, in this inflator, thereare the following problems.

In this inflator, even the small chamber 18 is maintained in apressurized atmosphere. In paragraph 24 of the description of thepublication, there is such a description that “P2 is approximately equalto or slightly smaller than (P1-Pm)”. Here, P2 represents a rupturingpressure for rupturing the rupturable plate 22, P1 represents arupturing pressure for rupturing the rupturable plate 16, and Pmrepresents a charging pressure of a gas charged in the small chamber 18and the main chamber 20. Considering the content of this disclosure,when the pressure in the small chamber 18 becomes higher than that inthe main chamber 20 due to activation of the initiator 30, there occursno problem when the two rupturable plates 16 and 22 are simultaneouslyruptured. However, in case that the rupturable plate 22 has beenruptured first, since the pressure in the small chamber 18 escapes tothe main chamber 20, a pressure rising in the entire of the smallchamber 18 and the main chamber 20 becomes small, so that the rupturableplate 16 is not ruptured and an air bag can not be normally inflated.Further, the rupturable plate 16 is not provided in the extension of theadvancing direction of the impact wave at the time of activation of theinitiator 30, which obviously is less reliable in view of rupturing therupturable plate.

FIG. 3 of the same publication discloses a structure in which an igniteris disposed such that its distal end is directed to the rupturable plate16. However, since a pressurized medium exists in the main chamber 20and the small chamber 18 separately, two rupturable plates are required,which makes the structure complicated.

In USP2002/0093182, an inflator which ruptures a rupturable plate 9 byprojecting of a piston 23 has been disclosed, as shown in FIGS. 1 to 3.The paragraph 28, the following description and FIG. 4 clearly explainthat a hole 17 c is formed in a portion of the periphery of a member 17accommodating an igniter 11, an end portion of a member 21 is entwistedtherein and the piston 23 is disposed inside. However, with such aprojectile mechanism of the piston 23, the number of parts is increasedand maintenance of size accuracy is complicated because of many smallparts, and there is still room for improvement in theses points.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an inflator in which amounting work to a module can be performed easily and reliability inactivation of the inflator is enhanced.

The invention described in claim 1 provides, as one means for solvingthe above problem, an inflator comprising a cylindrical inflator housingwhich is closed at one end thereof and is opened at the other end and inwhich a pressurized gas is charged, and a diffuser portion which isconnected to an opening portion of the inflator housing, accommodates anigniter and has a gas discharge port, wherein

-   -   at least one portion of a gas discharge passage existing from        the inflator housing to the gas discharge port of the diffuser        portion is closed by a flat plate-shaped rupturable plate;    -   an igniter for rupturing the rupturable plate is disposed such        that an axial direction of the inflator housing is orthogonal to        an axial direction of the igniter and the axial direction of the        igniter is not exactly opposite to a surface of the flat        plate-shaped rupturable plate; and    -   a means for directing a rupturing energy generated by activation        of the igniter in the exactly opposite direction to rupture the        rupturable plate.

The rupturable plate is mounted to an opening portion of the inflatorhousing or inside the diffuser portion. The rupturable plate is like aflat plate to be mounted, but it receives a pressure of a pressurizedgas to be deformed into a bowl-like shape after the pressurized gas ischarged.

Since the igniter is disposed such that the axial direction of theinflator housing and the axial direction of the igniter are orthogonalto each other, the entire inflator can be made compact as compared witha case that, when the igniter is mounted in the same axial direction asthe axial direction of the inflator housing, an additional member forgas discharging is required.

When the inflator is connected to a module in which an air bag isaccommodated, it is eventually connected to a portion of the gasdischarge port of the diffuser portion. However, when the igniter ismounted in the same manner as the present invention, a lead wireconnected to an igniter can be extended in an opposite direction to theair bag, so that the lead wire does not interfere with a moduleconnection at a time of mounting the inflator to the module.

By arranging, inside the diffuser, a means (for directing a rupturingenergy to act) for discharging a rupturing energy (an integrated energyproduced by an impact wave, a pressure rising and the like) generated byactivation of the igniter in the same direction as the axial directionof the inflator housing inside the diffuser, even if a rupturing energyfrom the igniter is dispersed, it can be focused on the rupturableplate, so that the rupturing ability of the rupturable plate can beenhanced.

The invention described in claim 2 is constituted in the inventiondescribed in claim 1 such that the igniter has a fragile portion at aportion exactly opposite to the rupturable plate, the fragile portion isruptured at an activation of the inflator and a rupturing energy acts onthe rupturable plate from the fragile portion.

Since the igniter (an electric type igniter) has an igniting portionprovided with a priming and the igniting portion is covered with a cupmade from aluminum or the like, by providing the fragile portion in thecup, an ignition energy (rupturing energy) is discharged from thefragile portion when the igniter is activated.

The invention described in claim 3 is constituted in the inventiondescribed in claim 2 such that the fragile portion provided in theigniter is constituted with a combination of a hole(s) provided in aside face of a cup member covering the igniting portion of the igniterand a sealing tape closing the hole(s) from the inside of the cupmember.

When the igniter is activated, the sealing tape is broken by a rupturingenergy to open a hole(s) and the rupturing energy is discharged from thehole(s) towards the rupturable plate.

The invention described in claim 4 is constituted in the inventiondescribed in claim 2 such that the fragile portion provided in theigniter comprises a portion surrounded by a groove or a portion providedwith a notch, which is provided in a side face of a cup member coveringthe igniting portion of the igniter.

The portion surrounded by the groove, which serves as the fragileportion, is one such as, for example, a groove formed in a circularshape (a continuous groove or a dotted line groove, which does notperforate). In the case of the circular groove, a portion defined by thecircular groove of the cup wall receives a rupturing energy to fall offin a circular shape and to produce a hole. And the rupturing energy isdischarged from the hole towards the rupturable plate.

The portion with a notch, which serves as the fragile portion, is onesuch as, for example, a notch formed in a cross shape in the cup (acontinuous notch or a dotted line notch which does not perforate). Inthe case of a notch like a cross mark, a notch in the cup wall receivesa rupturing energy and the cup wall is turned up at four sides toproduce a hole, and the rupturing energy is discharged from the holetowards the rupturable plate. Incidentally, it is preferable that thenotch is sealed by a thin sealing tape or the like in order to prevent apriming from leaking from the notch portion or prevent moisture fromentering therefrom. Alternatively, the notch is not a cross mark, but itmay be a perforating notch formed as an annular broken line.

The invention described in claim 5 is constituted in the inventiondescribed in claim 1 such that a guiding passage for guiding a rupturingenergy discharged from the igniter to the rupturable plate is formed inthe diffuser portion, and a rupturing energy is guided to a centralportion of the rupturable plate or a portion thereof near the centralportion by action of the guiding passage.

As long as the guiding passage can guide a rupturing energy to therupturable plate securely, its shape, structure or the like is notlimited to a specific one. By providing such a guiding passage, therupturable plate is ruptured unfailingly and easily.

In the invention described in claim 6, it is preferable that the guidingpassage for guiding a rupturing energy discharged from the igniter tothe rupturable plate comprises a cap which surrounds at least theigniting portion of the igniter and is disposed in the directionorthogonal to the axial direction of the inflator housing and a holewhich is provided at a position, on a side face of the cap, which iscorrectly opposed to the rupturable plate.

The shape and the structure of the cup are not limited specifically, andit may be a cylindrical cap which surrounds the igniting portion of theigniter at its one end opening portion and abuts on an inner wall faceof the diffuser portion at the other end opening portion.

Since the cap is positioned in the gas discharge passage, the diameterof the cap is set to be smaller than the diameter of the gas dischargepassage not to block a smooth flow of the pressurized gas. It is furtherpreferable that the length of the cap is also adjusted as well as thediameter of the cap.

The invention described in claim 7 is constituted in the inventiondescribed in claim 1 such that a cap which surrounds at least theigniting portion of the igniter and is disposed in a directionorthogonal to the axial direction of the inflator housing is provided,

-   -   a groove or a notch formed in a desired shape is provided at a        portion, in a peripheral face of the cap, which is exactly        opposite to the rupturable plate; and    -   a portion of the cap having the desired shape is deformed to        fall down towards the rupturable plate and come in contact with        the rupturable plate by action of a rupturing energy discharged        from the igniter.

In the invention described in claim 7, it is preferable that the desiredshape portion formed by the groove or the notch has an arrowhead shapefor making it easy to rupture the rupturable plate.

In the inventions described in claims 7 and 8, the rupturable plate isruptured by a multiplier effect of an impact due to collision to thedeformed portion of the cap, impact of a rupturing energy itselfdischarged from the hole produced at the deformed portion and anincrease of an internal pressure. Alternatively, the rupturable platemay by ruptured only by the impact due to a collision to the deformedportion of the cap.

Since the deformed portion is integrated with the cap before activationof the igniter in this manner, such a member as the independent pistonshown in USP 2002/0093182 is not required. Further, in case of rupturingthe rupturable plate by the multiplier effect, the plate is not rupturedby a single means such as a piston in the above prior art, so that thedeformed portion dose not have to be necessarily thick.

The invention described in claim 9 is constituted in any one of claims 1to 8 such that the pressurized gas is charged in a single space.

By charging the pressurized gas in the single space, the structure andassembling of the inflator can be simplified because the charging of thepressurized gas can be achieved rapidly at a time.

The invention described in claim 10 provides, as another means forsolving the above problem, an inflator comprising a cylindrical inflatorhousing which is closed at one end thereof and is opened at the otherend and in which a pressurized gas is charged, and a diffuser portionwhich is connected to the opening portion of the inflator housing,accommodates an igniter therein and has a gas discharge port, wherein

-   -   at least one portion of a gas discharge passage existing from        the inflator housing to the gas discharge port of the diffuser        portion is closed by a flat plate-shaped rupturable plate, and        the pressurized gas is charged in a single space;    -   an igniter for rupturing the rupturable plate is disposed in the        single space charged with the pressurized gas such that the        axial direction of the inflator housing and the axial direction        of the igniter obliquely cross with each other; and    -   a means causing a rupturing energy generated by activation of        the igniter to act in an oblique direction to the rupturable        plate to rupture the rupturable plate.

The angle defined between the axial direction of the inflator housingand the axial direction of the igniter is preferably an acute angle,more preferably an angle of 60° or less, further preferably an angle of50° or less, and especially preferably an angle of 40° or less.

The invention described in claim 10 can make the whole inflator furthercompact compared with the inventions described in claims 1 to 9.Further, in the invention described in claim 10, the same effect as thatin the invention described in claim 1 can also be achieved. Furthermore,by charging the pressurized gas in the single space, the structure ofthe inflator can be simplified.

The invention described in claim 11 is constituted in the inventionsdescribed in claims 1 to 10 such that a diffuser tube having a secondgas discharge port is further connected to the gas discharge port of thediffuser portion.

By using the above diffuser tube, mountability of the inflator to themodule can be improved by adjusting the diameter or the length of thediffuser tube according to the shape of the module while maintaining theshape of the diffuser portion unchanged.

The invention described in claim 12 is constituted in the inventiondescribed in claim 11 such that the diffuser tube is arranged such thatthe diffuser tube is coaxial to the inflator housing or the central axisof the inflator housing and the central axis of the diffuser tube areparallel to each other.

In the inventions described in claims 11 and 12, the diffuser tube hasplural second gas discharge ports in a peripheral face thereof, and itis preferable that the plural second gas discharge ports are providedcircumferentially at equal intervals.

By forming the gas discharge ports in this manner, even when theinflator is activated due to a fire or the like and the pressurized gasis ejected from the gas discharge port during transportation to storageof the inflator, the inflator is prevented from jumping out like arocket. For example, when only a single gas discharge port is provided,the inflator jumps out like a rocket due to ejection of the pressurizedgas, which is much dangerous.

The invention described in claim 14 is constituted in the inventionsdescribed in claims 1 to 13 such that a filter which catches fragmentsof the rupturable plate is disposed in the gas discharge passageexisting from the rupturable plate to the gas discharge port or to thesecond gas discharge port.

According to the inflator of the present invention, an inflator can bemade compact entirely and a mounting workability of the inflator to amodule during assembling of an air bag system can be improved. Further,since a rupturing ability of a rupturable plate at the time of actuationof an inflator is improved, the reliability of the inflator can be moreimproved as a product.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial partially sectional view of an inflator;

In FIG. 2, FIG. 2(a) is an axial partially sectional view of an inflatorand FIG. 2(b) is a radial partially sectional view of the inflator;

In FIG. 3, FIG. 3(a) is an axial partially sectional view of an inflatorand FIG. 3(b) is a radial partially sectional view of the inflator;

In FIG. 4, FIG. 4(a) is an axial partially sectional view of aninflator, FIG. 4(b) is a radial partially sectional view of theinflator, and FIG. 4(c) is a radial partially sectional view showing anactivation state of the inflator;

In FIG. 5, FIG. 5(a) is an axial partially sectional view of an inflatorand FIG. 5(b) is a radial partially sectional view of the inflator; and

FIG. 6 is an axial partially sectional view of an inflator.

DESCRIPTION OF NUMERALS

-   10, 100, 200, 300, 400, 500 inflator-   12 inflator housing-   19 rupturable plate-   20 diffuser portion-   21 gas discharge port-   26 igniter-   27 filter-   30 diffuser tube-   50 air bag

PREFERRED EMBODIMENT OF THE INVENTION (1) Embodiment 1

One embodiment will be explained with reference to FIG. 1. FIG. 1 is anaxial partially sectional view of an inflator 10.

A cylindrical inflator housing 12 has an opening portion at one end, andthe other end closed. The inner space 14 thereof is charged with apressurized medium comprising an inert gas such as argon, helium or thelike, or a nitrogen gas at the maximum pressure of about 70,000 kPa.Such a pressurized gas is charged in only the inner space 14.

The inflator housing 12 may be produced by swaging or spinning a pipe,and an existent gas cylinder may be utilized as the inflator housing asit is. When the swaging work or the spinning work is applied to a pipe,the pipe is closed while a thin hole serving as a charging hole for apressurized gas is left at one end side thereof.

After the inflator housing 12 is connected with a diffuser portion 20, apressurized gas is charged from a clearance between the thin holeprovided on a peripheral face or a closed end face of the inflatorhousing 12 and a sealing pin inserted in the thin hole. Thereafter, theinflator housing 12 is welded at the sealing pin to be closedcompletely.

An outer shell of the diffuser portion 20 is formed of a diffuserportion housing 22 and an inner space 24 thereof constitutes a gasdischarge passage.

On one end of the diffuser 20 is connected to an opening portion 16 ofthe inflator housing 12 and the other end thereof is provided with gasdischarge ports 21. A filter 27 made of a wire mesh or the like isprovided inside the gas discharge ports 21. An outer connection portionof the inflator housing 12 and the diffuser portion 20 is welded andfixed.

A disc-shaped rupturable plate 19 is mounted in a connection portionbetween the opening portion 16 of the inflator housing 12 and thediffuser portion 20 by welding and fixing a peripheral edge 19 a thereofto a peripheral edge of the opening portion of the inflator housing 12.A pressurized gas inside the inflator housing 12 is prevented fromflowing out before actuation of the inflator 10 by the rupturable plate19.

Since the rupturable plate 19 receives a pressure of the pressurized gasto be deformed in like a bowl projecting towards the diffuser portion 20and an apex of the projecting portion is positioned at the centralportion of the rupturable plate 19, a portion of the rupturable plateincluding the central portion is ruptured to open a closed gas dischargepassage at the time of actuation of the inflator 10.

An electric type igniter 26 is accommodated inside the diffuser portion20 having an igniting portion projected inside the inner space 26maintained at a normal pressure. The igniter 26 is mounted such that thecentral axis of the igniter 26 and the central axis of the inflatorhousing 12 are orthogonal to each other, and the igniter 26 is fixed bycrimping one portion 22 a of the diffuser portion housing 22.

The igniting portion of the igniter 26 is covered with a cup 28, a hole29 is provided in a peripheral face of the cup 28, and the hole 29 isclosed, from the inside, by a sealing tape made of aluminum to form afragile portion. The hole 29 and the rupturable plate 19 (the centralportion of the rupturable plate 19) are exactly opposite to each other.

The fragile portion can be formed by providing a portion surrounded by agroove or a portion having a notch on a side face of the cup 28 insteadof a combination of the hole 29 and the sealing tape. The portionsurrounded by a groove is one such as a groove (a continuous groove or adotted-line groove) formed in a circular shape and the portion having anotch is one such as a notch (a continuous notch or a dotted-line notch)formed in a cross shape on the cup.

One portion of the igniter 26 is protruded outside the inflator 10, theprotruded portion of the igniter 26 is fitted to a connector 23, and theconnector 23 is connected with a lead wire 25 for sending an activationsignal and a current to the igniter 26. A direction in which the leadwire 25 extends is different from a mounting direction of an air bag 50but it is coincident with an axial direction of the inflator housing 12.

In the inflator 10, since the extending direction of the lead wire 25can be restricted in this manner, the air bag 50 does not interfere witha wiring work of the lead wire 25 during assembling an air bag systemincluding the inflator 10. On the contrary, the lead wire 25 does notinterfere with a work for mounting the inflator 10 to the module.

The diffuser portion 20 is connected with the diffuser tube 30 coaxiallywith the inflator housing 12, and the inner space 31 constitutes a gasdischarge passage.

The diffuser tube 30 is connected to the diffuser portion 20 such thatit encloses the gas discharge port 21 at one end opening portion thereofand the diffuser tube 30 has plural second gas discharge ports 32 on aperipheral face of the other end portion thereof.

The plural number of second discharge ports are formed on the peripheralface of the diffuser tube 30 at equal intervals. The formation of theplural number of second discharge ports at equal intervals can include,for example, four ports formed at equal intervals of an angle of 90° C.,six ports formed at equal intervals of an angle of 60° C., eight portsformed at equal intervals of an angle of 45° C., as viewed from awidthwise section, and it may include a case that the number of thesecond gas discharge ports is an odd number if respective intervals areequal.

By arranging the plural second gas discharge holes 32 at equal intervalsin this manner, even when an inflator is actuated and the pressurizedgas is ejected from the second gas discharge holes 36 due to a fire orthe like during transportation to storage thereof, the inflator isprevented from jumping out like a rocket. The inner space 14 of theinflator housing 12, the inner space 24 of the diffuser portion 20 andthe inner space 31 of the diffuser tube 30 constitute a gas dischargepassage, and the pressurized gas inside the inflator housing 12 moves inthe above-described order to be discharged from the second gas dischargeports 32, thereby inflating and developing the air bag 50 mounted tocover the second gas discharge ports 32.

When the inflator 10 is actuated and the igniter 26 is activated, thepriming in the igniting portion is ignited and burnt to generate anigniting energy (a rupturing energy). Since the rupturing energy breaksthe sealing tape constituting the fragile portion of the cup 28 coveringthe igniting portion to open the hole 29, the rupturing energy isdischarged to be concentrated on the central portion of the rupturableplate 19 which is exactly opposite thereto. As a result, the rupturableplate 19 is instantaneously ruptured, and the pressurized gas in theinner space 14 moves through the gas discharge passage to be ejectedfrom the second gas discharge ports 32, thereby inflating the air bag50. Incidentally, since fragments of the rupturable plate 19 are caughtby the filter 27, the fragments are prevented from flowing into the airbag 50.

(2) Embodiment 2

Another embodiment will be explained with reference to FIGS. 2(a) and2(b). FIG. 2(a) is an axial partially sectional view of an inflator 100and FIG. 2(b) is a radial partially sectional view of a diffuser portion20 in FIG. 2(a).

The inflator 100 shown in FIG. 2 has a structure similar to the inflator10 shown in FIG. 1, and the same numerals as those in FIG. 1 are usedfor indicating the same parts in FIG. 2. Differences between thestructure in FIG. 2 and that in FIG. 1 will be explained.

As shown in FIG. 2(a), a cylindrical guiding passage 40 for guiding arupturing energy discharged from the igniter 26 to the rupturable plate19 is provided inside the diffuser portion 20. An opening portion of thecylindrical guiding passage 40 at one end encloses an igniting portionof the igniter 26 and an opening portion thereof at the other end isfitted in an circular hole 22 b provided in an inner wall face of thediffuser portion housing 22. An outer diameter of the cylindricalguiding passage 40 is substantially equal to an inner diameter of thecircular hole 22 b.

A guiding hole 42 is provided on a peripheral face of the cylindricalguiding passage 40 and at a position exactly opposite to the centralportion of the rupturable plate 19, and the guiding hole 42 is open.

The rupturable plate 19 is provided at a gas discharge port 21 which isa connection portion between the diffuser portion 20 and the diffusertube 30. For this reason, the pressurized gas is charged in a singlespace comprising the inner space 14, the cylindrical guiding passage 40in communication with the inner space 14 through a guiding hole 42, andthe inner space 24.

A cylindrical filter 27 is provided inside the second discharge ports 32provided in the diffuser tube 30.

Incidentally, as shown in FIG. 2(b), since an outer diameter of thecylindrical guiding passage 40 is adjusted not to close the inner space24 constituting the gas discharge passage, movement of the pressurizedgas is not prevented.

When the igniter 26 is activated, a priming in the igniting portion isignited and burnt to produce an igniting energy (a rupturing energy).After the rupturing energy is discharged into the cylindrical guidingpassage 40, it is discharged from the guiding hole 42 facing the centralportion of the rupturable plate 19. As a result, the rupturable plate 19is instantaneously ruptured, the pressurized gas inside the inner space14 and the inner space 24 moves through the gas discharge passage to beejected from the second gas discharge ports 32, thereby inflating an airbag. In this case, since fragments of the rupturable plate 19 are caughtby the filter 27, the fragments are prevented from flowing into the airbag.

(3) Embodiment 3

Another embodiment will be explained with reference to FIGS. 3(a) and3(b). FIG. 3(a) is an axial partially sectional view of an inflator 200and FIG. 3(b) is a radial partially sectional view of a diffuser portion20 in FIG. 3(a).

The inflator 200 shown in FIG. 3 has a structure similar to the inflator100 shown in FIG. 2, and the same numerals as those in FIG. 1 and FIG. 2are used for indicating the same parts in FIG. 3. Differences betweenthe structure in FIG. 3 and that in FIG. 2 will be explained.

In an inflator 200, since the opening portion 16 of the inflator housing12 is provided with the rupturable plate 19 and a pressurized gas ischarged in only the inner space 14, the inner space 24 is alwaysmaintained at normal pressure.

The guiding hole 42 of the cylindrical guiding passage 40 is provided ata position exactly opposite to the central portion of the rupturableplate 19.

The inflator 200 operates in the same manner as the inflator 100 so thatthe same effect as that in the inflator 100 can be achieved.Incidentally, in this embodiment, such a structure is employed that adischarge amount of pressurized gas is adjusted at the gas dischargeport 21 by throttling the diameter of the gas discharge port 21. Asimilar structure can be applied in the other embodiments. Besides,adjustment of the gas discharged amount can be conducted at the secondgas discharge ports 32, a clearance formed between the inner space 24and the cylindrical guiding passage 40, and the opening portion 16 ofthe inflator housing 12.

(4) Embodiment 4

Another embodiment will be explained with reference to FIGS. 4(a), 4(b)and 4(c). FIG. 4(a) is an axial partially sectional view of an inflator300, FIG. 4(b) is a radial partially sectional view in a diffuserportion 20 shown in FIG. 4(a), and FIG. 4(c) is a view for explaining anoperation state of the inflator 300.

The inflator 300 shown in FIG. 4 has a structure similar to the inflator10 shown in FIG. 1, and the same numerals as those in FIG. 1 are usedfor indicating the same parts in FIG. 4. Differences between thestructure in FIG. 4 and that in FIG. 1 will be explained.

As shown in FIG. 4(a), a cap 50 for rupturing the rupturable plate 19utilizing a rupturing energy discharged from the igniter 26 is providedinside the diffuser portion 20. The cap 50 surrounds the ignitingportion of the igniter 26 at a side of an opening portion thereof and aclosed end face thereof does not abut on an inner wall face 22 c of thediffuser housing 22 and a distance is provided between the closed endface and the inner wall surface.

As shown in FIG. 4(b), an arrowhead like deformed portion, comprisingfour-side notches, is provided in a peripheral surface of the cap 50 atthe position facing the center of the rupturable plate 19. Since a notchis not provided at a proximal end portion of the arrowhead-shapeddeforming portion 52, the arrowhead-shaped deforming portion 52 is notfallen off from the peripheral face of the cap 50.

Incidentally, as shown in FIG. 4(c), by forming a distal end portion ofthe arrowhead-like deforming portion 52 in a slightly curved shape inadvance, a contact area of the arrowhead-shaped deforming portion 52with the rupturable plate 19 becomes small and the arrowhead-shapeddeforming portion can apply a stronger impact to the central portion ofthe rupturable plate 19 so that the rupturing ability of the rupturableplate can be increased.

The rupturable plate 19 is provided at the gas discharge port 21 whichis a connection portion between the diffuser portion 20 and the diffusertube 30. For this reason, the pressurized gas is charged in a singlespace comprising the inner space 14, the inner space of the cap 50 whichis in communication via the notch, and the inner space 24.

A cylindrical filter 27 is provided inside the second gas dischargeports 32 provided in the diffuser tube 30.

Incidentally, as shown in FIG. 4(b), since the outer diameter and thelength of the cap 50 are adjusted not to close the inner space 24constituting the gas discharge passage, movement of the pressurized gasis not blocked.

When the inflator 300 is actuated and the igniter 26 is activated, thepriming in the igniting portion is ignited and burnt to generate anigniting energy (a rupturing energy). Since the rupturing energy isdischarged in the cap 50 and an internal pressure is increased, thenotched arrowhead-shaped deforming portion 52 is pressed.

As shown in FIG. 4(c), the pressed arrowhead-shape deforming portion 52deforms to fall down to the rupturable plate 19 and collide against therupturable plate 19. The rupturable plate 19 is instantaneously rupturedby a multiplier effect of an impact due to collision with thearrowhead-shaped deforming portion 52, an impact of the rupturing energyitself discharged from the hole produced after the arrowhead-shapeddeforming portion 52 is fallen down, and the increase in the internalpressure.

As a result, the pressurized gas in the inner space 14 and the innerspace 24 moves the gas discharge passage to be ejected from the secondgas discharge ports 32 and inflate an air bag. Incidentally, fragmentsof the rupturable plate 19 are caught by the filter 27, the fragmentsare prevented from flowing into the air bag.

(5) Embodiment 5

Another embodiment will be explained with reference to FIGS. 5(a) and5(b). FIG. 5(a) is an axial partially sectional view of an inflator 400and FIG. 5(b) is a radial partially sectional view of a diffuser portion20 in FIG. 5(a).

An inflator 400 shown in FIG. 5 has a structure similar to the inflator300 shown in FIG. 4, and the same numerals as those in FIGS. 1 and 4 areused for indicating the same parts in FIG. 5. Differences between thestructure in FIG. 5 and that in FIG. 4 will be explained.

In the inflator 400, the opening portion 16 of the inflator housing 12is provided with the rupturable plate 19 and a pressurized gas ischarged in only the inner space 14, so that the inner space 24 ismaintained at normal pressure.

An arrowhead-shaped deforming portion 52, comprising four-side notches,is provided on a peripheral face of the cap 50 at a portion thereoffacing the center of the rupturable plate 19. Since a notch is notprovided at a proximal end portion of the arrowhead-shaped deformingportion 52, the arrowhead-shaped deforming portion 52 is not fallen offfrom the peripheral face. The arrowhead-like deforming portion 52 may beformed to have a slightly curved shape at a distal end portion like thecase shown in FIG. 4(c).

The inflator 400 operates in the same manner as the inflator 300 so thatthe same effect as that in the inflator 300 can be achieved.

(6) Embodiment 6

Another embodiment will be explained with reference to FIG. 6. FIG. 6 isan axial partially sectional view of an inflator 500.

The inflator 500 shown in FIG. 6 has a structure similar to the inflator10 shown in FIG. 1, and the same numerals as those in FIG. 1 are usedfor indicating the same parts in FIG. 6. Differences between thestructure in FIG. 6 and that in FIG. 1 will be explained.

The igniter 26 is mounted such that the central axis of the igniter 26becomes oblique to the central axis of the inflator housing 12.

An angle defined between the central axis of the igniter 26 and thecentral axis of the inflator housing 12 is an acute angle, and it ispreferably 60° or less, more preferably 50° or less, and furtherpreferably 40° or less.

The rupturable plate 19 is provided at the gas discharge port 21 whichis the connection portion between the diffuser portion 20 and thediffuser tube 30. For this reason, a pressurized gas is charged in asingle space comprising the inner space 14 and the inner space 24.

The cylindrical filter 27 is provided inside the second gas dischargeport 32 provided in the diffuser tube 30.

As apparent from comparison between the inflator 500 shown in FIG. 6 andthe inflators shown in FIG. 1 to FIG. 5, in the inflator 500, the actingdirection of the rupturing energy from the igniter 26 is not exactlyopposite to the rupturing plate 19 but the rupturable plate 19 and theigniting portion of the igniter 26 are much close to each other, so thatrupturing ability to the rupturable plate 19 is high, and the igniter 19is mounted in an oblique direction to the central axis of the inflatorhousing 12, so that the whole inflator can be made further compact.

An air bag system using the inflator of the present invention can bemounted as an air bag system where each of the inflator shown in FIG. 1to FIG. 6 is used and an activation signal-outputting means comprisingan impact sensor and a control unit is combined with a module case inwhich each of the inflators shown in FIG. 1 to FIG. 6 and an air bag areaccommodated.

The inflator of the present invention can be applied to variousinflators such as an air bag inflator for a driver side, an air baginflator for a passenger side, an inflator for an air bag for a sidecollision, an inflator for a curtain air bag, an inflator for aknee-bolster, an inflator for an inflatable seat belt, an inflator for atubular system, and an inflator for a pretensioner.

1. An inflator comprising a cylindrical inflator housing which is closedat one end thereof and is opened at the other end and in which apressurized gas is charged, and a diffuser portion which is connected toan opening of the inflator housing, accommodates an igniter therein andhas a gas discharge port, wherein at least one portion of a gasdischarge passage existing from the inflator housing to the gasdischarge port of the diffuser portion is closed by a flat plate-shapedrupturable plate, an igniter for rupturing the ruptruable plate isdisposed such that the axial direction of the inflator housing isorthogonal to the axial direction of the igniter and the axial directionof the igniter is not exactly opposite to a surface of the flatplate-shaped rupturable plate, and a means for directing a rupturingenergy generated by activation of the igniter in the exactly oppositedirection to rupture the rupturable plate.
 2. An inflator according toclaim 1, wherein the igniter has a fragile portion at a portion exactlyopposite to the rupturable plate, the fragile portion is ruptured atactivation of the inflator and a rupturing energy acts on the rupturableplate from the fragile portion.
 3. An inflator according to claim 2,wherein the fragile portion provided in the igniter is constituted witha combination of a hole provided in a side face of a cup member coveringthe igniting portion of the igniter and a sealing tape closing the holefrom the inside of the cup member.
 4. An inflator according to claim 2,wherein the fragile portion provided in the igniter comprises a portionsurrounded by a groove or a portion with a notch, which is provided in aside face of a cup member covering the igniting portion of the igniter.5. An inflator according to claim 1, wherein a guiding passage forguiding a rupturing energy discharged from the igniter to the rupturableplate is formed in the diffuser portion, and a rupturing energy isguided to a central portion of the rupturable plate or a portion thereofin the vicinity of the central portion by action of the guiding passage.6. An inflator according to claim 5, wherein the guiding passage forguiding a rupturing energy discharged from the igniter to the rupturableplate comprises a cap, which surrounds at least the igniting portion ofthe igniter and is disposed in a direction orthogonal to the axialdirection of the inflator housing, and a hole which is provided at aposition, on a side face of the cap, which is exactly opposite to therupturable plate.
 7. An inflator according to claim 1, comprising a capwhich surrounds at least the igniting portion of the igniter and isdisposed in a direction orthogonal to the axial direction of theinflator housing is provided wherein, a groove or a notch formed in adesired shape is provided at a portion, in a peripheral face of the cap,which is exactly opposite to the rupturable plate; and a portion havingthe desired shape is deformed to fall down towards the rupturable plateand come in contact with the rupturable plate by action of a rupturingenergy discharged from the igniter.
 8. An inflator according to claim 7,wherein the desired shape portion formed by the groove or the notch hasan arrowhead shape, and the arrowhead-shaped portion is deformed to falldown towards the rupturable plate and come in contact with therupturable plate by action of a rupturing energy discharged from theigniter.
 9. An inflator according to any one of claims 1 to 8, whereinthe pressurized gas is charged in a single space.
 10. An inflatorcomprising a cylindrical inflator housing which is closed at one endthereof and is opened at the other end and in which a pressurized gas ischarged, and a diffuser portion which is connected to an opening portionof the inflator housing, accommodates an igniter therein and has a gasdischarge port, wherein at least one portion of a gas discharge passageexisting from the inflator housing to the gas discharge port of thediffuser portion is closed by a flat plate-shaped rupturable plate, andthe pressurized gas is charged in a single space; an igniter forrupturing the rupturable plate is disposed in the single space chargedwith the pressurized gas such that the axial direction of the inflatorhousing and the axial direction of the igniter obliquely cross with eachother; and a means causing a rupturing energy generated by activation ofthe igniter to act in an oblique direction to the rupturable plate torupture the rupturable plate.
 11. An inflator according to any one ofclaims 1 to 10, wherein a diffuser tube having a second gas dischargeport is further connected to the gas discharge port of the diffuserportion.
 12. An inflator according to claim 11, wherein the diffusertube is arranged such that the diffuser tube is coaxial to the inflatorhousing or the central axis of the inflator housing and the central axisof the diffuser tube are parallel to each other.
 13. An inflatoraccording to claim 11 or 12, wherein the diffuser tube has plural secondgas discharge ports in a peripheral face thereof and the plural secondgas discharge ports are provided circumferentially at equal intervals.14. An inflator according to any one of claims 1 to 13, wherein a filterwhich catches fragments of the rupturable plate is disposed in the gasdischarge passage existing from the rupturable plate to the gasdischarge port or to the second gas discharge port.